1. Field of the Invention
The subject invention generally pertains to loading dock seals and more specifically one that is vertically movable.
2. Description of Related Art
When an exterior doorway of a building is used as a loading dock for vehicles, especially trucks, the perimeter of the doorway often includes a dock seal. Dock seals close off gaps that would otherwise exist between the exterior face of the building and the back end of the truck. This allows cargo from the rear of the truck to be loaded or unloaded while dockworkers and the cargo are protected from the weather. Usually two side seals run vertically along the lateral edges of the doorway, and a top or head seal runs horizontally along the doorway's upper edge.
A typical dock seal comprises a resiliently compressible foam core protected by a fabric outer cover. Sealing is provided by backing the truck up against the seal, so that the seal compressively conforms to the rear shape of the truck. The foam core provides the necessary compliance and resilience to repeatedly conform to the shape of various trucks, while the outer cover protects the foam core from dirt, water and wear.
The greatest wear on the outer cover often occurs during the loading and unloading of a truck parked against the dock seal. Adding or removing cargo and/or driving a forklift on and off the truck bed may cause the rear of the truck to rise or lower a few inches, due to the truck's suspension. The rear of the truck rubbing tightly against the pad can tear the pad's cover or at least shorten its life significantly.
To address this problem, various dock seals have been developed with some success. For example, the Kinnear division of the Harsco Corporation of Columbus, Ohio has provided a compressible dock seal that moves vertically with vertical movement of the truck, thus minimizing abrasive rubbing between the two. With the Kinnear design, two side seals and the head seal are mounted to the face of a building by way of a track that allows the seals to move vertically with the truck, as the truck is being loaded or unloaded. However, since the head curtain is fixed relative to the side seals (and thus moves with the side seals), it appears that a clearance between the head seal and the building wall needs to be sealed or sheltered in some way. Otherwise, rainwater running down the wall could possibly seep behind the head seal and leak into the building. Moreover, since the head seal is between the two side seals, rather than extending over the top of them, gaps may exist between the ends of the head seal and the two side seals. To seal such gaps, and to seal the clearance between the head seal and the wall, apparently an additional cover or curtain is installed to overhang and cover the head seal and both side seals.
U.S. Pat. No. 4,015,380 discloses another dock seal that moves in response to vertical movement of the back of a vehicle. Here, the side seals include a corrugated sealing surface that is able to collapse and fold in the direction of the vehicle's movement. However, much of the seal's vehicle-responsive movement is provided by shifting of the sealing surface itself. Thus, it appears that much of the abrasive wear would still be concentrated at the sealing surface.
Other dock seals having a vertically movable head seal are disclosed in U.S. Pat. Nos. 5,775,044; 4,494,341 and 3,230,675. In each of these examples, however, the side seals appear to be fixed relative to the building wall.